A gyroscope is a device for measuring rotation. Gyroscopes are sometimes included in electronic devices, such as handheld electronic devices, in order to provide information about the orientation of such electronic devices. Such orientation information allows the electronic device to know information about its own physical position. The gyroscope may allow for recognition of movement within a three dimensional space. The electronic device may use such orientation information as an input signal. That is, the electronic device may be operated in a mode in which gyroscope measurements affect the operation of the electronic device.
Even when a gyroscope is not rotating, the gyroscope may have a signal output. The output, when the gyroscope is not rotating, is referred to as the bias or the bias error. Each sensing axis of the gyroscope may have a different bias. The bias may not be a fixed amount. That is, the bias may vary over time. Such variations may, for example, be caused by changes to the temperature of the electronic device or changes to the operating state of the electronic device. For example, the bias may be affected when the electronic device switches from an off state to an on state.
Gyroscope readings may also be subject to noise. Gyroscope readings may contain random fluctuations that are not due to movement of the gyroscope. That is, even when the gyroscope is stationary, the gyroscope readings obtained from the gyroscope may vary due to the effect of noise.
Like reference numerals are used in the drawings to denote like elements and features.